1. Field of the Invention
The present invention relates to motor vehicles and more particularly to auxiliary systems installed on a vehicle requiring increased vehicle engine power output for operation.
2. Description of the Problem
Contemporary trucks are often equipped with auxiliary systems that require increased engine output for operation. Examples of such auxiliary equipment are high output water pumps on fire trucks and trash compacting equipment on refuse collection vehicles. Trucks equipped with such auxiliary systems may therefore come equipped to support power takeoff operation (PTO) at the election of the driver or operator. Driver/operator control of PTO is often by a remote switch. By the term xe2x80x9cremotexe2x80x9d it is meant that such a switch is located on the vehicle away from the driver""s normal position in the cab.
Although some vehicles are set up for mobile PTO, more commonly an engine controller requires that the vehicle""s automatic transmission, if the vehicle is so equipped, be in neutral. Automatic transmissions are designed to be in neutral when a shift lever is in the neutral position. Transmission controllers can cause automatic transmissions to assume a neutral state under other conditions, for example when auto neutral operation is selected and the park brake is set, regardless of the position of the shift lever. Popular transmission controllers provide an indication both of when the transmission shift lever is positioned in neutral and when the transmission is in neutral (regardless of shift lever position). However, commercial vehicle regulations require explicit indication of shift lever position in neutral before allowing engine cranking. Since permission for engine cranking is controlled by an engine controller, common practice has been to tie the shift lever position indicative signal to the engine controller on a driveline disengage signal input pin. However, use of this port to indicate lever position leaves no avenue for telling the engine controller of other circumstances when the transmission is in neutral and PTO operation is allowable.
Under certain circumstances, the transmission may in fact be in neutral when the engine is running and the shift lever is not positioned in the neutral position. While under such circumstances cranking is neither permissible nor desirable, a driver/operator could be allowed to activate PTO. An automatic transmission that can move to neutral without repositioning the shift lever would be convenient for operators using PTO. What is needed is a PTO system which restricts engine cranking to circumstances where a transmission gear select shift lever has been moved to neutral, but allows PTO when the transmission is in neutral, regardless of shift lever position.
According to the invention there is provided an apparatus for installation on a vehicle having an automatic transmission, a gear select lever, an engine, and an engine cranking system, which allows operation of an auxiliary system by the engine when the automatic transmission is in neutral, regardless of the position of the automatic transmission gear select lever, and cranking of the engine when the gear select lever for the automatic transmission is positioned at neutral. The apparatus provides a selection mechanism independent of the transmission gear select lever for placing the automatic transmission in a neutral state independent of the position of the gear select lever. A transmission controller provides for generation of a signal indicating the state of the automatic transmission. Further provided are a source for a signal indicating the position of the gear select lever. An independent source of a request signal for increased engine power output for power takeoff operation is connected to an engine controller. The engine controller provides fuel flow control to the engine for setting power output in response to the state of the request signal for increased engine power output and further in response to the signal state on a driveline disengage signal input. A relay connected to the means for generating a signal indicating automatic transmission state for setting a driveline disengage signal. The engine controller is further responsive to the driveline disengage signal for setting a engine crank inhibit signal level. A crank inhibit relay responsive to appropriate states of the engine crank inhibit signal and the signal indicating the position of the gear select lever provides for enabling engine cranking.
Additional effects, features and advantages will be apparent in the written description that follows.